Buggy code:
public class SemanticAnalyzer implements ASTVisitor { private VariableEnvironment variableEnv ; private FunctionEnvironment functionEnv ; private TypeEnvironment typeEnv ; public SemanticAnalyzer ( ) { } public Object VisitNewArrayExpression ( ASTNewArrayExpression newarrayexpression ) { } public Object VisitClasses ( ASTClasses classes ) { } public Object VisitAssignmentStatement ( ASTAssignmentStatement assignstatement ) { Type lhs = ( ( Type ) ( assignstatement . variable ( ) . Accept ( this ) ) ) ; Type rhs = ( ( Type ) ( assignstatement . value ( ) . Accept ( this ) ) ) ; if ( lhs != rhs ) { <START_BUG> CompError . message ( assignstatement . line ( ) , ( "Lefthand<seq2seq4repair_space>side<seq2seq4repair_space>and<seq2seq4repair_space>righthand<seq2seq4repair_space>" + "side<seq2seq4repair_space>of<seq2seq4repair_space>and<seq2seq4repair_space>assignement<seq2seq4repair_space>statemetn<seq2seq4repair_space>must<seq2seq4repair_space>match." ) ) ; <END_BUG> } return null ; } public Object VisitArrayVariable ( ASTArrayVariable arrayvariable ) { } public Object VisitBooleanLiteral ( ASTBooleanLiteral boolliteral ) { } public Object VisitClass ( ASTClass asclass ) { } public Object VisitInstanceVariableDef ( ASTInstanceVariableDef variabledef ) { } public Object VisitClassVariable ( ASTClassVariable classvar ) { } public Object VisitForStatement ( ASTForStatement forstatement ) { } public Object VisitEmptyStatement ( ASTEmptyStatement emptystate ) { } public Object VisitDoWhileStatement ( ASTDoWhileStatement dowhile ) { } public Object VisitFormal ( ASTFormal formal ) { } public Object VisitFormals ( ASTFormals formals ) { } public Object VisitFunction ( ASTFunction function ) { } public Object VisitFunctionCallExpression ( ASTFunctionCallExpression callexpression ) { } public Object VisitFunctionCallStatement ( ASTFunctionCallStatement statement ) { } public Object VisitInstanceVariableDefs ( ASTInstanceVariableDefs variabledefs ) { } public Object VisitNewClassExpression ( ASTNewClassExpression classexpression ) { } public Object VisitOperatorExpression ( ASTOperatorExpression opexpression ) { } public Object VisitFunctionDefinitions ( ASTFunctionDefinitions fundefinitions ) { } public Object VisitReturnStatement ( ASTReturnStatement returnstatement ) { } public Object VisitPrototype ( ASTPrototype prototype ) { } public Object VisitUnaryOperatorExpression ( ASTUnaryOperatorExpression unaryexpression ) { } public Object VisitStatements ( ASTStatements statements ) { } public Object VisitVariableExpression ( ASTVariableExpression varexpression ) { } public Object VisitVariableDefStatement ( ASTVariableDefStatement varstatement ) { } public Object VisitProgram ( ASTProgram program ) { } public Object VisitWhileStatement ( ASTWhileStatement whilestatement ) { } public Object VisitIntegerLiteral ( ASTIntegerLiteral literal ) { } public Object VisitBaseVariable ( ASTBaseVariable base ) { } public Object VisitIfStatement ( ASTIfStatement ifsmt ) { } }

Fix:
CompError . message ( assignstatement . line ( ) , ( "Lefthand<seq2seq4repair_space>side<seq2seq4repair_space>and<seq2seq4repair_space>righthand<seq2seq4repair_space>" + "side<seq2seq4repair_space>of<seq2seq4repair_space>and<seq2seq4repair_space>assignement<seq2seq4repair_space>statement<seq2seq4repair_space>must<seq2seq4repair_space>match." ) ) ;